Alternating-current circuit interrupters



Jan. 3, 1956 G. w. PRISTSAK 2,729,723

ALTERNATING-CURRENT CIRCUIT INTERRUPTERS Filed Feb. 16, 1953 2 Sheets-Sheet 1 Inventor.-

Jan. 3, 1956 G. w. PRISTSAK 2,729,723

ALTERNATING-CURRENT CIRCUIT INTERRUPTERS Filed Feb. 16, 1953 2 Sheets-Sheet 2 We, 1 I

INVENTOR. m A/MM A A M ATTORNEY United States Patent Ofilice ALTERNATlNG-CURRENT CIRCUIT INTERRUPTERS Gustav Wilhelm Pristsalr, Berlin-Spandau, Germany, assignor to Siemens-Schuckertwerke Aktiengesellschaft, Berlin-Siemensstadt, Germany, a German ccrporation My invention relates to circuit breakers, contactors and other interrupting devices for alternating-current which, for circuit interruption, draw an are between sepating contacts and subject the arc to extinguishing conditions.

In the conventional interrupters, the extinction of the arc, as a rule, is effected or promoted by extraneous cooling and/or by subjecting the arc to elongation.

It is among the objects of my invention to devise an interrupting device that secures a reliable arc extinction at a smaller arc voltage and hence a smaller are energy than attainable in the known devices under otherwise similar operating conditions.

To this end, and in accordance with a feature of my invention, I provide each arc gap of an alternating-current interrupting device with a movable contact whose separating travel from the stationary contacts extends only up to about the distance needed for making the gap dielectrically resistant to the reignition voltag and I dispose one or more pairs of mutually spaced burn-off or runoff electrodes adjacent to the contacts and in such a relation thereto that the short are originating between the separating contacts is displaced to the run-off electrodes and is caused to travel along the runner gap of the electrodes until it becomes extinguished by the natural zero passage of the alternating current. The blowing effect inherent in the arc circuit or additional artificial means, for instance, magnetic blowing devices may be used for thus displacing the arc. The spacing between the run-oil electrodes is uniform along the arc travel path so that the arc, during its movement, is not subjected to appreciable elongation; and the minimum of the available path for the progressive or, as will be shown, reversible travel of the arc between the run-ofi electrodes, is at least as long as the distance that the travel of the arc may span during a half-wave period of the alternating current.

To minimize or prevent elongation of the shifting arc, and according to another feature of my invention, I further provide means for constraining the-arc travel along a predetermined line and direction and, preferably, also as to the width or volume that the are at any moment may occupy. More specifically, such arc guiding or restraining means may comprise a particular shape and electric connection of the run-off electrodes which results in the formation of magnetically effective current loops through the arc or its root points. The definite directioning and, as the case may be, the constraint imposed upon the location and width of the arc travel, offer protection from undesired expansion of the switching fire and also permit giving the arc extinguishing arrangement smaller dimensions than otherwise applicable.

Like interrupting devices gap or interrupter pole. According to another feature of the invention, the run-off electrodes are carried by the wall structure of such an arc chamber. It is then possible to select for the arc chamber walls any suitable material 2,729,723 Patented Jan. 3, 1956 which need not be insulating but, for instance, may also consist of metal.

A device according to the invention may have a single set of run-off electrodes for each interrupting gap. For use with higher voltages, however, several sets of run-off arranged in each line or pole of the circuit to be interrupted. In the latter case, each individual gap, during the interrupting performance, contributes virtually instantaneously to the build-up of the necessary dielectric gap strength. The displacement of the resulting individual arcs then occurs in different directions between the individual systems of electrodes.

The normally current-conducting main contacts are subjected to wear if the movable contact can perform bouncing movements when contacting the stationary contacts during the circuit closing operation. To avoid such wear, and in accordance with another feature of my invention, the weight of the parts to be moved during the switching operation may be reduced by placing the stationary contacts as close as possible to each other so that only a relatively short bridging contact is required. To secure with such a design a sufiicient dielectric strength or voltage resistance between the live contacts in the open condition of the device, insulated partition walls, prefersupply buses. distance into several gaps, thus increasing the voltage safety of the device.

According to a further feature of the invetnion, the spacing between the run-off electrodes may be made adjustable. The adjusting means may operate in a constrained connection with the operating means for the movable main contact so that the adjustment is automatically effected together with the interrupting operation and occurs either at the beginning or shortly after the completion of this operation.

When applying a device according to the invention for high power capacities, it may be of advantage to avoid sharp edges, corners or curvatures on the electrodes to prevent giving cause to high local field strengths or to evaporation of metal tending to maintain the arc gaps in ionized and conductive condition.

The foregoing and other objects, advantages and features of my invention will be apparent from the following description in conjunction with the embodiments of my invention exemplified by the drawings in which:

Fig. 1 shows schematically the interrupting device of a circuit breaker with two pairs of arc run-off electrodes;

Fig. 2 is a front view and Fig. 3 a side view thereof taken along the line AB illustrating another interrupt- Figs. 6 and 7 are modifications, being comparable with Fig. 5 and oth serially subdivided arcs.

The circuit breaker device according to Fig. 1 has two separation gaps for one conductor line or interrupter pole. Two fixed contact pieces 1 and 2 are integral with respective current supply buses 3, 4 and form L- shapedstructures together with the buses. A movable open position of contact is such that the gap spacing between contact 5 and respective contacts 1 and 2 corresponds to only about the gap voltage at which the arcs, after extinction at current Zero, will not reignite. Only a short travel distance is required for reaching this condition. For instance, in circuit breakers for current from power lines of the customary voltage (for instance 110 volts, 220 volts, 440 volts or more, at 50 C. P. S. or 60 C. P. S.) this distance may amount to only one to five millimeters depending upon the electrical conditions of the circuit to be interrupted. Such a short travel can readily be produced at a high operating speed especially if the movable mass is kept small. For minimizing this mass, the two stationary contact structures are placed as close together as safely permissible, and the flash-over strength between them is increased by insulated partition plates 6a and 6b mounted between the contact structures. Two burn-off or run-oil electrodes 7 and 8 are disposed in parallel relation with two respective counter electrodes 1a and 2a which are formed by respective lateral extensions of the fixed contact pieces 1 and 2. The two electrodes 7 and 8 are electrically interconnected by a lead 9.

When the movable contact 5 during the circuit breaking performance is separated from the fixed contact pieces 1 and 2, two arcs are drawn at 10 and 11 respectively. These arcs displace themselves, or are additionally displaced by magnetic blowing means (not illustrated), in the outward direction and run between the electrodes 1a and 7, and between the runner electrodes 2a and 8, then passing through the arc positions shown at 10 and 11 respectively. During the displacing travel, the arcs are practically not subjected to elongation. They continue running until the alternating current passes through zero at which moment both arcs are extinguished. The travel distance for the displacing run of the arcs between the electrodes in, 7 or 2a and 8 must, therefore, be so dimensioned that the arcs, taking into account the arc displacing speed, can traverse the entire available distance within a half-wave period of the alternating current. The electrode spacing, and hence the width of the runner gaps, is as small as the spacing between the fully separated interrupter contacts. The electrodes 1a, 2a, 7 and 8 are designed and are given the cross section needed for a good dissipation of the heat developed at the root points of the arcs.

The length of the structure to provide for the necessary run-off travel of the arc may be reduced according to the invention by providing a limiting'device acting on the current-loop principle along the distance through which the arc may pass during its displacing movement between each pair of runner electrodes. An example of a circuit breaker equipped with such a device is shown in Fig. 2.

In Fig. 2 the stationary contacts 1 and 2 are again joined with the pertaining current supply buses 3 and 4 and cooperate with a movable bridge contact 5. In contrast to Fig. 1, however, the arc runner electrodes in the breaker according to Fig. 2 are subdivided into two L-shaped conductor portions, each comprising two pairs of electrodes in, 7a, and 1b, 712 or 2a, 8a, and 2b, 812. These pairs of electrodes are aligned opposite the horizontal leg portions of the L-shapes whose vertical legs are formed by the fixed contacts 1, 2 alone or in conjunction with the pertaining current supply buses 3, 4. The stationary contacts and all electrodes are firmly mounted on a common supporting structure (not shown). Electrodes 7a, 7b, 8a, 8b are all electrically interconnected by a conductor 9. Electrode 1b is connected with bus 3 by a conductor 12, and electrode 2b is connected with bus 4 by a conductor 13. The individual electrodes are furthermore recessed or grooved at their rear portions, as can be most clearly seen by the dotted-line representation in Fig. 2, to obtain the current-loop biasing efiect hereinbelow described.

When the movable bridging contact Sis being separated from the fixed contacts 1 and 2, two arcs will first develop at 10 and 11 respectively. Due to current-loop action and, if desired, by the action of additional magnetic blowing, the two arcs run outwardly into the runner gaps between electrodes in, 7a and 2a, 811. When arc 10 transfers to electrode 7a, it remains subjected to outwardly directed blowing. This is because the conductor 9 and the contact 1 are electrically joined with respective electrodes 7a and 1a at points located at the entrance of the runner gap so that the are forms immediately part of a new loop circuit through lead 9, and this loop circuit imposes on the are a moving force of unaltered direction. Hence arc 10 now shifts outwardly through the position 10', and arc 11, for analogous reasons, travels outwardly through the position 11.

If the arcs are not extinguished by occurrence of current zero, then the arc 10 may transfer from electrodes Ia, 7a to electrodes 11), 7b where it may pass through the position 10". Immediately after the transfer moment, the arc becomes part of another loop circuit through conductors 12, 9 and electrodes 1b, 7b. However, since the transferred arc first burns between the inward ends of the electrodes while the arc-current supply conductors 12 and 9 are connected to respective points at the outward ends of the electrodes, the loop at the arc has now a direction opposed to the loop direction previously eifective.

Consequently, the loop circuit now brakes and then reverses the arc travel and drives the arc back toward the electrodes 1a, 7a. Should the arc, when still burning, jump back to the electrodes in and 70, it again forms part of the previously effective loop of outwardly directed blowing action. 1

As a result of the braking and reversing effects of electrodes 1b and 7b, and analogously of the electrodes 2b and 8b, it is no longer necessary to provide for a travel path as long as is needed in a design according to Fig. 1 to keep the arc in travelling motion for a halfwave period of the alternating current or such earlier time of natural extinction by the Zero passage of the current.

With the running span of the arc thus limited, it may be desirable to prescribe for the arc a definite travel path also in the lateral direction, that is perpendicular to the plane of illustration of Fig. 2, sothat the arc cannot dodge and elongate in a lateral direction. An embodiment of such a design is shown in Fig. 3 which may be considered as a lateral sectional view of the device of Fig. 2.

According to Fig. 3, the electrodes collectively denoted in Fig. 2 by 2b and 8b respectively, single parts but are each composed of a pair of horizontally arranged partial electrodes 2b and 2b", or 8b. and 8b. Each of these partial electrodes is so shaped and has preferably a current-supply lead connected at such a point that an are occurring, for instance, between parts 2b and 8b is subjected to current-loop action toward the right as is indicated by an arrow placed in Fig. 3 between electrodes 2b and 8b. If the arc jumps to electrodes 22:" and 8b, it is subjected to current-loop action toward the left. Consequently, the travel of the arc, shifting alternately between the pairs of partial electrodes, is confined to an area close to, or between the mutually opposite electrode faces. Thus, the are when travelling through the runner gaps, is guided along the center line of the system so that a definite travel path and direction are secured. Such arrangements for the directional control of the arc travel path may also be provided on the fixed contacts 1 and 2 and on the bridging contact 5, as is shown in Fig. 2 on contacts 1 and 2.

In devices of the kind described with reference to Figs. 2 and 3, the horizontal electrodes, for instance 2b and 2b", may be combined to a structurally integral unit. To this end, these electrodes may form two L shap'ed structures which are connected with each other at the top by a transverse piece and which have their horizontal do not consist of free ends located opposite each other. Figs. 4 and 5 illustrate such a modification.

The circuit breaker according to Figs. 4 and 5 has two generally L-shaped structures 14 and 15 Whose respective horizontal portions enter into the space of two stationarily mounted hollow bodies 16 and 17. All parts that coact during the switching performance have a generally tubular shape of substantially rectangular cross section with an opening in the bottom side. The hollow bodies are further provided with incisions or slits 18, 19 to thus form the pairs of horizontally arranged partial electrodes. The electrodes connected with the currentsupply buses 14 and 15 are further equipped with horizontal slots 14b and 14c, or 15b and 150 to form L- shaped run-01f electrodes for driving and braking the arc. This particular design, requiring a horizontal slot, is not used for electrodes 16a, 16b and 17a, 17b, since for some purposes the illustrated design is sufficient for securing the desired interrupting effect.

Electrodes 16 and 17 are electrically interconnected by a conductor 20. An are which may occur between the electrodes 14 and 16 (or 15 and 17) at their lateral, vertical limbs, is driven downwardly by current-loop action into the slits 18, 19 of parts 14 and 16 or 15 and 17.

Since parts 16 and 17 have the same electric potential, they may also be combined to a single body which is to be given an opening for the insertion of the two vertical legs of the L-shaped contact structures 14 and 15, and an opening for the bridging contact 21 to cooperate with the stationary contact pieces 14a and 15a. The illustrated bridging contact 21 is so arranged that the slit of its tubular cross section lies at the top. Arcs occurring between parts 14a and 21 or between parts 15a and 21, after the bridging contact has moved downward until its horizontal limbs are about level with the lower horizontal limbs of the parts 16, 17 (see Fig. 5), are driven by blowing action into the hollow bodies and run between the centers of parts 14 and 16, or 15 and 17, until the arcs reach the recesses 18 and 19 of both contact systems, where the horizontal displacing movement of the arcs is terminated. At these places the arcs extinguish at a natural current zero passage. Up to the extinguishing moment, the arc may alternately jump between the electrodes 16a and 16b, or 17a and 17b, coacting with the corresponding counter electrodes along the horizontal parts of structures 14 and 15, as has been explained with reference to Figs. 2 and 3.

Such an electrode system may be further equipped with a housing structure as represented in cross section in Fig. 6. This structure is obtained by inserting the outer electrodes 22 (correspondingto part 16 in Figs. 4, 5) into a U-shaped or box-shaped housing 23. This housing may consist completely of metal. The are chamber space in which the interrupting performance takes place 'is then fully enclosed, openings being preferably provided only for the escape of arcing vapors.

The shape of the outer electrodes may be modified according to Fig. 7. This design comprises a housing whose walls 24, 25 form directly part of the electrodes corresponding to parts 16 and 17 in Figs. 4 and 5. To this end, the walls 24 and 25 carry mutually spaced hollow bolts 26 and 27 with closed and outwardly rounded front faces. These cup-shaped bolts serve as run-off electrodes and for forming the arc-displacing current loops. They are inserted or rivetted into the walls 24 and 25 and face each other at their respective free ends. These ends lie opposite the electrodes connected to the supply buses, for instance opposite electrode 28 corresponding to electrodes 16 in Fig. 4.

The walls 24 and 25 may also form the side portions of a frame-shaped or annular, rectangular cross section of aprismatic housing with openings for the insertion of the stationary current-supply buses and for the passage of the movable bridging contact. This housing may be subdivided preferably in a plane parallel to the switch contacts 14 and 15 according to Fig. 4, or in Fig. 7 perpendicular to the plane of illustration, the plane of division extending between the electrodes 26 and 27 for facilitating the assembling of the circuit breaker. When assembling the breaker, the two halves of the housing are to be moved toward each other into the closed position for then surrounding and enclosing the electrodes, such as electrode 28 in Fig. 7 or electrodes 14, 15 in Fig. 4.

The hollow structures that form pairs of electrodes accordingito Figs. 4 to 7 need not necessarily have the abovementioned, substantially rectangular cross section but may also be given any suitable different shape, for instance, that of a cylindrical tube.

As mentioned, a faster recovery of the dielectric strength and resistance of the arc gap during the interrupting performance can be secured according to the invention by providing a plurality of series arranged arc gaps in each pole or line of the breaker. An example of such an interrupter is illustrated in Fig. 8.

According to Fig. 8, two stationary L-shaped contact structures 44 and 45 have horizontal extensions which form respective electrodes. The contact portions of the structures 44 and 45 cooperate with a movable bridging contact 46. Two run-off electrodes 47, 48, and 49, 50 are disposed opposite each electrode extension of the contact structures 44 and 45. These run-01f electrodes, designed for instance in the shape of studs or bolts according to Fig. 7, may, if desired, also operate as braking electrodes. Intermediate electrodes 51 and 52 are disposed between the respective two sets of run-off electrodes and the electrode extensions of structures 44 and 45. The electrodes 51 and 52 are insulated from structures 44, 45 as well as from the electrodes 7 to 50. The run-off electrodes 47 to 50 are all conductively interconnected. During the interrupting operation, an arc 53 occurring for instance between main contacts 44 and 46 is driven outwardly and, when passing between the run-off electrodes, is subdivided into two series arranged partial arcs 54 and 55.

When the series arcs transfer to electrode 48 and the opposite electrode-face portion of structure 44, the arcs become subjected to a braking action due to the fact that they now form part of a loop of reversed blowing direction. The reversal in blowing direction is obtained by virtue of the shape of the recess 44' or 45 which has the effect of supplying the arc current at a point outwardly away from the root of the are shifting, for instance, from position 54 to the left beyond the opening of recess 44.

When designing a circuit breaker according to the invention, it may be found that the arc run-elf electrodes, for most favorable operation, should be given a smaller mutual spacing than is permitted by now applicable safety regulations and standards concerning the required minimum spacing between the breaker contacts when in the fully open position. In such cases, any standards seemingly adverse to best performance in accordance with the invention may nevertheless be satisfied by making the paired run-oif electrodes movable relative to each other. This may be done by constrainedly moving one of the two electrodes away from the other under control by the actuating mechanism that moves the movable contact to the circuit opening position. The electrode movement may be set to occur at the beginning, during, or after the interrupting performance. Of course, for securing best operating conditions, it may generally be favorable to make the electrode spacing adjustable or correctable.

Experience with circuit breakers according to the invention has shown that for the control of power current; under normal operating conditions in power lines, a travel distance of the movable main contact in the order of l to 5 millimeters is sufficient. It has further been found that in many cases the interruption is completed by extinction of the are occurring within the first pair of runofi electrodes following the main breaker contacts in the running direction of the arc. Consequently, if desired,

these first run-elf electrodes may already serve to perform the arc travel inhibiting and reversing function.

It will be obvious to those skilled in the art upon a study of this disclosure that devices according to my invention may be given a large variety of designs and modifications, and may be embodied in structures other than those specifically illustrated and described, without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

1. A device for interrupting alternating current, con prising two stationary contacts and a movable contact bridgingly engageable with said two stationary contacts and movable away therefrom to form two primary arc gaps with said respective stationary contacts, two pairs of electrodes forming two respective interstitial runner gaps of substantially uniform gap spacing and disposed adjacent to said respective primary arc gaps on opposite sides thereof to receive in said runner gaps the arcs originating in said respective primary arc gaps, a first conductor connecting one electrode of each pair with one of said respective stationary contacts at an electrode end away from said primary gaps, and a second conductor interconnecting said other two electrodes at respective electrode points away from the electrode ends adjacent to said primary gaps, whereby an arc entering into one of the runner gaps forms together with said two conductors a loop circuit tending to reverse the running direction of the arc.

2. A device for interrupting alternating current, comprising stationary contact means, a movable contact member engageable with said contact means and separable therefrom to form primary arc gap, two pairs of electrodes forming two respective interstitial gaps of substantially uniform gap spacing aligned with each other and with said primary gap to define together an arc travel path, conductor means electrically connecting one electrode of each of said pairs with said stationary contact means and connecting the two other electrodes with each other, said conductor means having at the electrode pair adjacent to said primary gap 21 point of connection located close to said primary gap to provide arc-blowing action away from said primary gap, and said conductor means having with the other electrode pair a point of connection located away from said primary gap for arc-blowing action toward said primary gap.

3. A device for interrupting alternating current, comprising two stationary contacts and a movable contact bridgingly engageable with said two stationary contacts and movable away therefrom to form two primary arc gaps with said respective stationary contacts, two pairs of electrodes forming two respective interstitial runner gaps of substantially uniform gap spacing and disposed adjacent to said respective primary arc gaps on opposite sides thereof to receive in said runner gaps the arcs originating in said respective primary arc gaps, one electrode of each pair being electrically connected with one of said respective stationary contacts, the other two electrodes being electrically connected with each other, an arc chamber structure enclosing said gaps and having conductive chamber walls, and conductor means connecting said electrodes with said contact means to form blow-action loop circuits together with the arc, said walls forming part of said conductor means.

4. A device for interrupting alternating current, comprising two stationary contacts and a movable contact bridgingly engageable with said two stationary contacts and movable away therefrom to form two primary arc gaps with said respective stationary contacts, two pairs of electrodes forming two respective interstitial runner gaps of substantially uniform gap spacing. and disposed adjacent to said respective primary arc gaps on opposite sides thereof to receive in said runner gaps the arcs originatingin said respective primary arc gaps, one electrode of each pair being electrically connected with one of said respective stationary contacts, the other two electrodes being electrically connected with each other, an arc chamber structure of metal enclosing said gaps and having bare metal surfaces in its interior, and conductor means connecting said electrodes with said contact means to form blow-action loop circuits together with the arc, said conductor means being integral with said chamber structure.

5. A device for interrupting alternating current, comprising two stationary contacts and a movable contact bridgin ly engageable with said two stationary contacts and movable away therefrom to form two primary arc gaps with said respective stationary contacts, two pairs of electrodes forming two respective interstitial runner gaps of substantially uniform gap spacing and disposed adjacent to said respective primary arc gaps on opposite sides thereof to receive in said runner gaps the arcs originating in said respective primary arc gaps, one electrode of each pair being electrically connected with one of said respective stationary contacts, the other two electrodes being electrically connected with each other, an arc chamber structure enclosing said gaps and having conductive chamber walls, said electrodes having respective currentsupply conductors and forming respective L-shaped electrode structures together with said conductors, and said L-shaped structures being mounted on said chamber walls in conductive connection therewith so as to form blowaction loop circuits together with the arcs in said runner gaps.

6. A device for interrupting alternating current, comprising two stationary contacts and a movable contact bridgingly engageable with said two stationary contacts and movable away therefrom to form two primary arc gaps with said respective stationary contacts, two pairs of electrodes forming two respective interstitial runner gapsof substantially uniform gap spacing and disposed adiac'ent to said respective primary arc gaps on opposite sides thereof to receive in said runner gaps the arcs originating in said respective primary arc gaps, one electrode of each pair being electrically connected with one of said respective stationary contacts, the other two electrodes being electrically connected with each other, and an arc chamber structure of metal enclosing said gaps, said electrodes being cup shaped and having their respective open ends conductively secured to said structure.

7. A device for interrupting alternating current, comprising two stationary contacts and a movable contact bridgingly engageable with said two stationary contacts and movable away therefrom to form two primary arc gaps with said respective stationary contacts, two pairs of electrodes forming two. respective interstitial runner gaps of substantially uniform gap spacing and disposed adjacent to said respective primary arc gaps on opposite sides thereof to receive in said runner gaps the arcs orig inating in said respective primary arc gaps, one electrode of each pair being electrically connected with one of said respective stationary contacts, the other two electrodes being electrically connected with each other, each of said stationary contacts having a current supply bus and forming with said bus a substantially L-shaped structure of which one leg is assigned to said contact and the other to said bus, said two L-shaped structures having their contact legs extending in opposite directions and aligned with each other and having their bus legs spaced in parallelrelation to each other, and conductive partitions disposed between said bus legs in parallel and in sulated relation to said bus legs and to each other.

References Cited in the file of this patent UNITED STATES PATENTS 1,851,238 Branchu Mar. 29, 1932 2,356,039 Ellis et al Aug. 15, 1944 2,534,069 Schleicher Dec. 12, 1950 2,629,036 Brown Feb. 17, 1953 2,632,074 Herman Mar. 17, 1953 

